CARSON — For more than two decades, at least one undrafted rookie has made the Chargers’ regular-season roster. JJ Jones made his case for that spot on Saturday night.

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Just before halftime of the Chargers’ preseason debut at StubHub Center, Jones exploded up the middle of the field. He eluded two tacklers almost immediately, then weaved toward the right sideline to lose a couple more. By the time he reached the opposing 30-yard line, no one had chance to catch him.

“I ended up seeing the kicker,” Jones said. “I knew when I saw the kicker, it was over. The kicker would never tackle me. I was going to take it all the way.”

The 72-yard punt return touchdown gave the Chargers an eight-point lead against the Seahawks in what turned out to be a 24-14 victory.

It also slammed on the defibrillator on Jones’ chances to make the 53-man active roster on Sept. 1.

At just 5-foot-10, 173 pounds, Jones is currently the lightest man in the Chargers’ locker room, weighing in two pounds below fellow wideout Travis Benjamin. As an undersized Division II product out of West Georgia, he might not add much to a receiving corps that already includes Pro Bowler Keenan Allen, former 1,000-yard receiver Tyrell Williams and former first-round pick Mike Williams. Factor in Benjamin — who had a punt return touchdown to go along with four scoring catches last season — and that likely leaves just one spot up for grabs.

But Jones also returned two kickoffs for 41 yards in the first half against the Seahawks. That’s an area where his team could use some help.

The Chargers averaged just 19.0 yards per kick return last season, ranking above only the 49ers (18.4) and Lions (18.2). They have not returned a kickoff for a touchdown since Dec. 30, 2012, when Micheal Spurlock scored a 99-yarder against the Raiders.

If Jones can prove his worth on special teams — perhaps lightening the load on Benjamin as the team’s primary punt returner — then the Chargers’ staff might give him a long look.

“I know I can make plays, but it’s a whole different speed coming from college to the NFL,” Jones said. “I just had to grasp the speed, grasp the confidence to do what I love to do.”

“Anybody in camp has a chance in my opinion,” Coach Anthony Lynn said earlier this week.

Lynn was responding to a question about tight end Je’Ron Hamm. After Saturday night, the answer might also apply to Jones.

FIRST SCORE

Mike Williams finally reached the end zone.

The 2017 first-round pick scored his first NFL touchdown on Saturday, hauling in a 25-yard pass from quarterback Geno Smith in the third quarter. Drafted No. 7 overall a year ago, Williams sat out his entire rookie training camp and preseason with a back injury. He also failed to score in 10 regular-season appearances, catching 11 passes for 95 yards.

This summer, Williams has looked like a different player. Even before his acrobatic grab at StubHub Center, the 6-foot-4, 220-pound target had generated buzz in practices, showing his potential as a big red-zone target.

“I needed it,” Williams said of his touchdown. “I felt like I was doing it in practice and I just needed to translate it to a game.”

INJURY REPORT

Defensive back Jaylen Watkins injured his knee in the second quarter on Saturday and (did not return). He put very little pressure on his right leg when trainers helped him to the sideline, and was soon carted to the locker room. He is scheduled to have an MRI on Sunday.

The 26-year-old started at free safety against the Seahawks, but opened the game by earning a flag for lowering his helmet.

Running backs Austin Ekeler (calf), Justin Jackson (hamstring) and Russell Hansbrough all sat out Saturday night’s preseason game. That left the Chargers with just two tailbacks on the depth chart: starter Melvin Gordon sat down to rest after three series, ceding most of the game to undrafted rookie Detrez Newsome.

Lynn said Ekeler was healthy enough to play in a regular-season game.

Pro Bowl defensive end Joey Bosa and starting cornerback Trevor Williams did not play due to minor foot and ankle injuries, respectively.

Rookie linebacker Kyzir White did not dress after dealing with knee soreness this week. Defensive back A.J. Hendy, who was dinged up in the preseason opener, sat out too. Also sidelined were receiver Dylan Cantrell (knee) and tight end Cole Hunt (ankle).

NOTES

Philip Rivers started at quarterback after sitting out the preseason opener. He led two drives and completed 6 of 7 passes for 62 yards. … Pro Bowl pass rusher Melvin Ingram made his mark against Seattle, terrorizing right tackle Germain Ifedi and forcing running back Chris Carson to fumble at the goal line. … Former Seahawks and USC assistant Rocky Seto was on the sideline with his family on Saturday. Seto is now a pastor at Evergreen SGV Church in La Puente. … Referee Tony Corrente was booed for saying, “Timeout, San Diego” in the final minute of the first quarter.